The present invention is directed towards a current/flow comparator for monitoring the rate of flow of coolant through a dynamoelectric machine. More particularly, the present invention is directed towards a current/flow comparator which generates an alarm signal whenever the instantaneous rate of flow of a coolant fluid cooling the armature of the dynamoelectric machine falls below a predetermined percentage of a desired instantaneous flow rate, which desired flow rate varies as a function of the square of the instantaneous current flowing through the armature.
In large dynamoelectric machines, a coolant liquid is circulated through the conductors of the armature bars of the dynamoelectric machine for the purpose of cooling the armature. Several schemes for circulating the coolant fluid are disclosed in the prior art and are not directly part of the present invention. Exemplary of such systems are U.S. Pat. No. 3,693,036 issued to Nikolas Schmitt and U.S. Pat. No. 2,695,368 issued to C. E. Kilbourne. In each of these cooling systems, the cooling fluid serves to remove heat generated by the relatively high current flowing through the armature of the dynamoelectric machine. The heat generated by this current varies as a function of the square of the armature current. Accordingly, the rate of flow of coolant through the armature conductors required to satisfactorily cool the armature also varies as a function of the square of the armature current.
As long as the flow rate of the coolant fluid remains within a predetermined percentage of the desired flow rate determined by the actual armature current, sufficient cooling will take place to enable satisfactory operation of the dynamoelectric machine.
A primary object of the present invention is to monitor the difference between the actual flow rate and the desired rate and to generate a first alarm signal whenever the actual flow rate falls below a first predetermined percentage of the desired flow rate. This signal may then be utilized to activate a human perceivable alarm which indicates that the flow rate of cooling fluid through the dynamoelectric machine should be manually increased.
A further object of the present invention is to generate a second, operative control signal when the flow rate falls below a second predetermined percentage of the desired flow rate. This signal may then be utilized to automatically adjust the loading of the dynamoelectric machine to insure that it will not be damaged by the heat generated in the armature thereof. Yet other objects of the present invention will become apparent from a reading of the following description of the invention.